The No. 7, which excelled its predecessors in length and bulk, was intended greatly to outstrip the best of them in velocity. The first air ship had attained fourteen miles per hour, the No. 6, nearly twenty miles an hour in winning the Deutsch prize, and over twenty miles per hour on subsequent occasions, though provided with a motor rated at only 12 horse power. The new vessel which had little greater resistance than No. 6, was to carry four times the internal pressure, or about 12 centimeters of water, and to be propelled by an engine of 60 horse power. The inventor expected therefore to attain a speed of between forty and fifty miles per hour. A very lofty expectation for that day, and one still unrealized for many years.
The racing air ship, or No. 7, was of cigar form, supporting a long car beneath, and generally resembling the No. 6, but slightly more tapering. Her length was six times her major diameter, and her volume 45,000 cubic feet. The envelope was made of two layers of the strongest French silk, four times varnished, and was built exceptionally thick at the stern, where the differential outward pressure is greatest in flight. The propulsion was effected by a 60 horse-power water-cooled four-cylinder Clément engine actuating two screw propellers 16½ feet in diameter, one in front the other at the rear of the car. The poise and maneuvering were to be controlled in the usual way, by means of the rudder and shifting weight. The inventor seemed not to realize that the bow of his vessel was too sharp to cleave the air with minimum resistance, though his predecessor, Jullien, in 1850, had discovered experimentally that a torpedo form is better for speed than the symmetrical spindle form used by Santos-Dumont in his racing vessel. He did, however, in time, learn that the torpedo form of hull is better for stability of forward motion, and hence adopted that form in his little Runabout.
The No. 9 was a thick torpedo-shaped air ship originally cubing only 7,770 feet, though later enlarged to 9,218 feet. It was so thick as to appear nearly egg-shaped. In order to make it respond promptly to the rudder Santos-Dumont drove it through the air blunt end foremost, but with apparent regrets, thinking that it would cleave the air more easily than sharp end foremost. In this he was mistaken; for the writer has shown that a body of such shape encounters much more resistance—roughly one hundred per cent more—when driven sharp end foremost than when driven blunt end forward. This fact furnishes one reason why most whales and swift fishes have blunt bows and long tapering sterns. However this be, the practical man felt his way to success, whether right or wrong in his theory of resistance. When actuated by a three horse-power Clément motor, weighing 26½ pounds, the little air ship carried its jaunty pilot twelve to fifteen miles an hour on many a merry trip about Paris and its environs.
The No. 10, or Omnibus, was a well shaped vessel of nearly eighty thousand cubic feet capacity, and amply provided with steering devices. Its hull tapered slightly from front to rear, terminating in projectile-shaped ends, and had a length of nearly six times its major diameter. Underneath was suspended a long car provided with aëroplane surfaces, in addition to the usual rudder, for controlling its movements.
Its arrow-like appearance was suggestive of some of the greatest German balloons of the decade. Indeed, the Omnibus, if well powered, might have proved a very swift vessel, in addition to a powerful carrier. But she was designed merely for easy going passenger service, for the purpose of popularizing aëronautics and stimulating its growth.
Santos-Dumont now had three typical air ships, a spacious and well equipped “aërodrome,” and ample facilities for advancing the science of motor balloons on a moderate scale. He could not, however, maintain the ascendency in this branch of science in France; for he encountered the rivalry of great wealth employing highly trained engineering and constructive talent. He could, however, still promote the art as a pioneer and a popularizer. This he continued to do. With his little Runabout he would one day guide-rope along the boulevard, another day take up a little boy, another day send up a beautiful young lady to navigate the air alone for a short distance, another day voyage over the military parade grounds and with his revolver fire a salute of twenty-one shots to the President of France, and give exhibitions to arouse the interest of the War Department. But he could not keep pace with the new giants in aëronautics, and he did not attempt it. Nor did he ever build a vessel of sufficient power, speed and durability to be purchased by the French nation. That honor went to his opulent contemporaries who had not failed to take cognizance of his contributions to the aërial art.
CHAPTER V
In 1899 the Lebaudy brothers, wealthy sugar refiners in Paris, commissioned their able engineer, Julliot, to make investigations and develop plans for a large and swift air ship. This he did with the assistance of Surcouf, a well-known manufacturer of balloons at Billancourt, Paris. Emulating the example of Santos-Dumont and certain German aëronauts in making their plan, they adopted the light petroleum engine for motive power, but experimented on a larger scale, thus creating a new era in military aëronautics in France. Their first vessel was the Jaune whose bag was built at Surcouf’s place, and its mechanical part at the Lebaudy Sugar Refinery. When launched, in 1902, it so pleased the owners that they determined to continue the experiments on a larger scale. Their second air ship, called the Lebaudy, after fulfilling various tests, was accepted by the French government and formed the beginning of its modern aërial fleet.
Moisson, near Paris, where the balloons were kept, now became quite an aëronautical center. Here, under military supervision and the skillful management of the aëronaut Juchmes, other dirigibles were built in rapid succession. Of these the Patrie was launched in 1906, and the République in 1908, both fine swift vessels capable of voyaging many hours and carrying many passengers. The Lebaudy vessels were the first air ships of the “semi-rigid type,” in which the long and flexible envelope, or hull, is provided with a rigid keel or floor, from which the car is suspended with its machinery and passengers. They are, therefore, of unusual interest both for their scientific design and for the stimulus they imparted to the growth of aërial fleets. For this reason they may well be studied in some detail.